In recent years, a power transmission control device including a stepped transmission having a plurality of gear positions and not having a torque converter, a clutch interposed between an output shaft of an internal combustion engine and an input shaft of the stepped transmission and capable of adjusting a clutch torque (the maximum value of the torque which can be transmitted by the clutch), and control means for controlling, by using actuators, the clutch torque and a gear position of the stepped transmission depending on a travel state of a vehicle has been developed (for example, see Patent Literature 1). This power transmission control device is also referred to as automated manual transmission (AMT).
In a vehicle equipped with the AMT, when a gear change action (action for changing a gear position of the transmission) is to be carried out, a state of the clutch is changed from an engaged state (clutch torque>0) to a disengaged state (clutch torque=0) before the start of the gear change action. While the clutch is maintained in the disengaged state, the gear change action is carried out. After the gear change action is finished, the clutch is returned from the disengaged state to the engaged state.
Further, in recent years, a so-called hybrid vehicle provided with an engine and an electric motor (an electric motor and an electric power generator) as power sources has been developed (for example, see Patent Literature 2). The hybrid vehicle may employ a configuration in which an output shaft of the electric motor is connected to any one of an output shaft of the internal combustion engine, an input shaft of the transmission, and an output shaft of the transmission. In the following description, a driving torque of the output shaft of the internal combustion engine is referred to as “internal-combustion-engine driving torque,” and a driving torque of the output shaft of the electric motor is referred to as “electric-motor driving torque.”